[Bindings] Create and use V8 context snapshots

third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp

Index: third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp b/third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp
index 8bda40f6bcd9854adbb96c4ecd3cf7189d3de56c..1be36bb0414c6a332a82b3c83e906e8a49f1580b 100644
--- a/third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp
@@ -39,6 +39,7 @@
 #include "bindings/core/v8/V8HTMLDocument.h"
 #include "bindings/core/v8/V8Initializer.h"
 #include "bindings/core/v8/V8PagePopupControllerBinding.h"
+#include "bindings/core/v8/V8SnapshotUtil.h"
 #include "bindings/core/v8/V8Window.h"
 #include "core/dom/Modulator.h"
 #include "core/frame/LocalFrame.h"
@@ -116,7 +117,7 @@ void LocalWindowProxy::DisposeContext(Lifecycle next_status,
 }
 
 void LocalWindowProxy::Initialize() {
-  TRACE_EVENT1("v8", "LocalWindowProxy::initialize", "isMainWindow",
+  TRACE_EVENT1("v8", "LocalWindowProxy::Initialize", "IsMainFrame",
                GetFrame()->IsMainFrame());
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER(
       GetFrame()->IsMainFrame()
@@ -137,6 +138,7 @@ void LocalWindowProxy::Initialize() {
   }
 
   SetupWindowPrototypeChain();
+  V8SnapshotUtil::SetupContext(context, GetFrame()->GetDocument());

[haraken, 2017/07/04 15:04:19]

SetupContext => InstallRuntimeEnabledFeatures ?

[peria, 2017/07/07 06:21:52]

Done.
sounds better.

 
   SecurityOrigin* origin = 0;
   if (world_->IsMainWorld()) {
@@ -157,25 +159,24 @@ void LocalWindowProxy::Initialize() {
     SetSecurityToken(origin);
   }
 
-  MainThreadDebugger::Instance()->ContextCreated(script_state_.Get(),
-                                                 GetFrame(), origin);
-  GetFrame()->Client()->DidCreateScriptContext(context, world_->GetWorldId());
-  // If conditional features for window have been queued before the V8 context
-  // was ready, then inject them into the context now
-  if (world_->IsMainWorld()) {
-    InstallConditionalFeaturesOnWindow(script_state_.Get());
+  {
+    TRACE_EVENT1("v8", "Notification", "IsMainFrame",

[haraken, 2017/07/04 15:04:19]

Notification => ContextCreationNotification

[peria, 2017/07/07 06:21:53]

Done.

+                 GetFrame()->IsMainFrame());
+    MainThreadDebugger::Instance()->ContextCreated(script_state_.Get(),
+                                                   GetFrame(), origin);
+    GetFrame()->Client()->DidCreateScriptContext(context, world_->GetWorldId());

[haraken, 2017/07/04 15:04:19]

Oh, the context creation notification still exits. Is the performance problem
already gone?

[peria, 2017/07/07 06:21:53]

Yes, as the closed issue http://crbug.com/v8/6175 shows,
they had instantiated console.log dynamically, and it is now builtin.
Time spent in "Notification" became ~10 times faster (1.5ms -> 0.16ms),
and this is no longer a performance bottleneck.

+    // If conditional features for window have been queued before the V8 context
+    // was ready, then inject them into the context now
+    if (world_->IsMainWorld()) {
+      InstallConditionalFeaturesOnWindow(script_state_.Get());
+      GetFrame()->Loader().DispatchDidClearWindowObjectInMainWorld();
+    }
   }
-
-  if (world_->IsMainWorld())
-    GetFrame()->Loader().DispatchDidClearWindowObjectInMainWorld();
 }
 
 void LocalWindowProxy::CreateContext() {
-  // Create a new v8::Context with the window object as the global object
-  // (aka the inner global). Reuse the outer global proxy if it already exists.
-  v8::Local<v8::ObjectTemplate> global_template =
-      V8Window::domTemplate(GetIsolate(), *world_)->InstanceTemplate();
-  CHECK(!global_template.IsEmpty());
+  TRACE_EVENT1("v8", "LocalWindowProxy::CreateContext", "IsMainFrame",
+               GetFrame()->IsMainFrame());
 
   Vector<const char*> extension_names;
   // Dynamically tell v8 about our extensions now.
@@ -190,11 +191,25 @@ void LocalWindowProxy::CreateContext() {
 
   v8::Local<v8::Context> context;
   {
+    v8::Isolate* isolate = GetIsolate();
+    Document* document = GetFrame()->GetDocument();
     V8PerIsolateData::UseCounterDisabledScope use_counter_disabled(
-        V8PerIsolateData::From(GetIsolate()));
-    context =
-        v8::Context::New(GetIsolate(), &extension_configuration,
-                         global_template, global_proxy_.NewLocal(GetIsolate()));
+        V8PerIsolateData::From(isolate));
+    TRACE_EVENT1("v8", "ContextCreation", "IsMainFrame",

[haraken, 2017/07/04 15:04:19]

Is this trace event useful? I guess that the trace event at line 178 would be
enough.

[peria, 2017/07/07 06:21:54]

I introduced this trace to confirm other tasks in
LocalWindowProxy::CreateContext() are light enough.
Now we know it correct, so I removed.

+                 GetFrame()->IsMainFrame());
+
+    v8::Local<v8::Object> global_proxy = global_proxy_.NewLocal(isolate);
+    context = V8SnapshotUtil::CreateContext(
+        isolate, World(), &extension_configuration, global_proxy, document);
+
+    if (context.IsEmpty()) {

[haraken, 2017/07/04 15:04:19]

Add a comment and explain when this can happen.

[peria, 2017/07/07 06:21:54]

Done.

+      v8::Local<v8::ObjectTemplate> global_template =
+          V8Window::domTemplate(isolate, *world_)->InstanceTemplate();
+      CHECK(!global_template.IsEmpty());
+      context = v8::Context::New(isolate, &extension_configuration,
+                                 global_template, global_proxy);
+      VLOG(1) << "A context is created NOT from snapshot";
+    }
   }
   CHECK(!context.IsEmpty());
 
@@ -211,6 +226,9 @@ void LocalWindowProxy::CreateContext() {
 }
 
 void LocalWindowProxy::SetupWindowPrototypeChain() {
+  TRACE_EVENT1("v8", "LocalWindowProxy::SetupWindowPrototypeChain",
+               "IsMainFrame", GetFrame()->IsMainFrame());
+
   // Associate the window wrapper object and its prototype chain with the
   // corresponding native DOMWindow object.
   DOMWindow* window = GetFrame()->DomWindow();
@@ -255,12 +273,15 @@ void LocalWindowProxy::SetupWindowPrototypeChain() {
 
 void LocalWindowProxy::UpdateDocumentProperty() {
   DCHECK(world_->IsMainWorld());
+  TRACE_EVENT1("v8", "LocalWindowProxy::UpdateDocumentProperty", "IsMainFrame",
+               GetFrame()->IsMainFrame());
 
   ScriptState::Scope scope(script_state_.Get());
   v8::Local<v8::Context> context = script_state_->GetContext();
   v8::Local<v8::Value> document_wrapper =
       ToV8(GetFrame()->GetDocument(), context->Global(), GetIsolate());
   DCHECK(document_wrapper->IsObject());
+
   // Update the cached accessor for window.document.
   CHECK(V8PrivateProperty::GetWindowDocumentCachedAccessor(GetIsolate())
             .Set(context->Global(), document_wrapper));
@@ -322,8 +343,8 @@ void LocalWindowProxy::SetSecurityToken(SecurityOrigin* origin) {
     String frame_security_token = frame_security_origin->ToString();
     // We need to check the return value of domainWasSetInDOM() on the
     // frame's SecurityOrigin because, if that's the case, only
-    // SecurityOrigin::m_domain would have been modified.
-    // m_domain is not used by SecurityOrigin::toString(), so we would end
+    // SecurityOrigin::domain_ would have been modified.
+    // domain_ is not used by SecurityOrigin::toString(), so we would end
     // up generating the same token that was already set.
     if (frame_security_origin->DomainWasSetInDOM() ||
         frame_security_token.IsEmpty() || frame_security_token == "null") {